INTRODUCTION 7 
which reach down from the five leaves next above. The 
leaves are deciduous and bear buds in their axils which 
develop in the following year. The majority of these buds, 
however, do not develop into long shoots, but remain 
stunted, and are called dwarf shoots. In these shoots the 
internodes do not lengthen, so that all the leaves borne 
by them are inserted very close together, and appear in 
a rosette. These dwarf shoots generally bear leaves for 
a number of years, and their age can be determined by 
counting the whorls of dark-brown bud-scales which remain 
attached at their bases. The dwarf shoots may, under 
favourable circumstances, grow out into long shoots, but 
they more commonly get left behind by the growth of the 
tree, and when they become too much shaded by other 
branches the shoots die and remain on the branches as 
tufts of brown bud-scales, until they are ultimately cast 
off the tree. 
Internal structure of the stem. This will be described 
in detail, as the stem forms the feeding ground for the 
mycelia of all the most important disease-causing fungi. 
As it will be necessary to introduce a number of botanical 
terms which could not be explained except at great length, 
readers who are unacquainted with the general features 
of a plant’s anatomy are recommended to omit this section 
and pass on to the general account of larch canker in the 
next chapter. 
If a first-year shoot, about 1:5 mm. in diameter, be cut 
in winter and a transverse section examined under the low 
power of a microscope, the tissues will be found to be 
arranged as in fig. 2. On the outside are five protrusions, 
the decurrent leaf-bases or ‘ leaf-cushions ’, between which 
are narrow furrows. The cushions are nearly 1 mm. in 
breadth and about 0:2 mm. in thickness. These cushions 
contain rather large resin ducts, one near each edge, which 
pass down from the leaves and end blindly in the cortex. 
Their length is one to four times that of an internode, so 
that any section may disclose their presence in one to four 
cushions. Not infrequently one resin duct in a cushion is 
